Polyphase synchronous motor.



B. e. LAMME. .POLYPHASE SYNCHRONOUS MOTOR'.

' APPLICATI ON FILED JAN. 1. 1911. 1,158

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UNITED srarns Partner @FFECE.

BENJAMIN G. LAIVJIME, 0F PITTSBURGH, PENNSYLVANIA, ASSIG'NOR T0 WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A COEIPOBATION OF PENN- SYLVANIA.

T 0 all whom/2'1 may concern Be it known that I, BENJAMIN G. LAMME, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new' and useful Improvement in Polyphase Synchronous Motors, of which the following is a specification.

My invention relates to synchronous dvnamoelectric machines and it has special reference to polyphase synchronous motors.

The object of my invention is to provide a machine of the class above indicated that shall operate satisfactorily and which,- at the same time, shall have the starting characteristics of a polyphase induction motor.

Self-starting synchronous motors are well known and have been in general use for a number of years. They are usually started by supplying polyphase alternating currents to the armature winding, the field structures being so designed that they will act as induction motor secondaries and give the desired starting torques. The field structure is usually arranged with a distributed type of grid or cage winding which acts as a damper at synchronous speed and as a starting winding while the motor is being accelerated. The'field winding proper renders little or no assistance in starting,'as'it is equivalent to a single phase winding. Each of the arrangements just referred to is open to the objection that it is necessarily a compromise of the best starting, synchronizing and operating conditions:v If a cage wind ing of very high resistance is employed, the starting conditions will be improved, but the motor will have considerable slip at full speed as an inductionmotor and, consequently, there is more difficulty in pulling it into synchronism. Furthermore, the winding is inferior as a damper under operating conditions by reason of its high rewhich the exciting circuit isiconnected, are also broughtout through collector rings. Atstarting, both. 5 of diametrically op- Specification of Letters Patent.

Application filed January 7, 1911. Serial No. 601,372.

through external resistances.

v nous characteristicsin the machine.

A pair of equi-potential poin ts,' preferably midway between the points to POLYPHASE SYNCHRQNGU S MOTOR.

PatentedNov.2,1915.

posite points are connected through external resistance, thereby producing a true polyphase induction motor with a symmetrical secondary winding that is closed lVhenmaXimum speed is attained, direct current exciting current is supplied to one group of collector rings, thereby producing synchro diagrammatic view of the windings and circuit connections for a machine arranged in accordance therewith. Fig. 2 is a similar view of a modified field winding showing the damper which forms a part of my invention, and Fig. 3 isa sectional elevation of a suitable structure for effecting the circuit changes that are indicated diagrammatically in Fig. 2.

Referring to Fig, 1 of the drawings, the armature winding 1 of a synchronous motor may be supplied with polyphase alternating current energy from any suitable source, such asthree phase line conductors 23i. The field magnet winding 5 of-the same machine is of the continuous or closed-"circuit tyne and, as shown, is provided with four taps 6, 7, 8 and 9 that are separated by approximately 90 electrical degrees. It is, of course, immaterial whether the armature or the field member rotates but, in accordance with the more usual arrangement, it is assumed that the field member is the rotatable and the armature the stationary part of the throw switch 21 being provided for the purpose of selecting between the resistor 18 and the eXciter 20. A switch 22 is adapted, when closed, to short-circuit the resistor 19.

For starting the motor :5 the sw tch.

In ad- I 21 is thrown into such position as to insert the resistor-18, the switch '22 is opened to synchronous speed is attained, the switch 21 trated, like-parts being'designated by theis reversed in position-to connect the direct current generator 20 across the taps (3 and 7 of the field winding. The switch, 22 may be closed, thereby establishing a low-resistance cross connection between the points 8 and 9 which are at equi-potential points in the winding. The motor is thus operated as a synchronous motor, the starting resistors 18 and 19 being entirely excluded and having no detrimental effect on the normal operation of the machinej a Referring to Fig. 2 of the drawings, an alternate form of field windingis here illussame-reference characters as in the'other figures of the drawings. In addition to the taps 6, 7, 8 and 9, which are connected to the slip rings, as before", I provide a series of cross connections 23 which join equipotentialpoints in the winding, when con-. sidered as the field winding of a synchro-' nous. motor,- and are open circuited while the machineis being started as. a polyphase' induction motor. Each of the cross connections 23 is provided with a SW 7 itch 24 which may beofa'ny suitable form.

In Fig-., 3 of the drawings, I have illustrated a structure Which, is suitablef'or effecting theopening and closing of the cross connections when the field member is the rotating part of the machine, but I do not wish to be limited to any specific means for accomplishing this purpose. Referring to Fig- 3; a magnetizable core member 25 is supported on a spider 26 and is provided 'with a closed-circuitwinding'which is in-.

dicated in the other figures by the reference character 5. The spider 26 is mounted on a shaft 27 which also supports a sleeve 28, a

sliding ring 25) and a sliding contact-closing member 30. The slip rings 1O, 11, 12' and 13 are mounted on and are insulated from the sleeve 28, to which a pair of insulating rings 31 and 32 are also secured. A set of contact segments 33 is secured to the outer surface of the ring 32 and a corresponding set of contact fingers 34 is secured to-the ring 31 to project over the segments 33 of the ring 32. The contact-closing member 30 is in the form of a disk having a flange 35 which is adapted to force the fingers 34 into engagement with the. corresponding segjusted on the-shaft '27. This adjustmentments 33 when the member 30 is axially admay be effected in any suitable way, a well known means comprising the Slldlng ring 29, anactuating lever 36 arid one or more connecting rods 37 being illustrated. The contact fingers 34 are-connected to suitable taps in the field winding, as indicated in the diagramof Fig. 2. I

WVhen the equi-potential points of. the two-circuit winding are connected. and the machine is operating as a synchronous motor, the connections serve the function of a daniperfand elfectively prevent hunting and other trouble which dampers are designed to overcome.

invention is not restricted to the use of a two-circuit winding for the field of the synchronous motor or to the use of the specific damping means here shown and described, and I desire that only such limitations shall be-imposed as are indicated in the appended claim.

I claim as my invention: A synchronous .motor comprising -'a distributed field magnet winding, resistorsed tions connected across pairs of diametrically opposite taps in said winding for starting and meansfor connecting one pair of said taps to a source of unidirectional current and for 'short-circuiting the resistor section corresponding to the other pair of. taps for, normally operating the'motor In. testimonyv whereof; I have hereunto subscribed my name this 29th day of Dec.,

1910.. BENJ G.LAMME.

Witnesses C. E. WILSON,

' B.) B. HINES. 

